feature-benchmark: Measure peak memory usage using various statistics (possibly including jemalloc, getrusage, etc.)

[def-]

Feature request

Instead of the currently used memory consumption at the end of the test. I think peak makes more sense, so we should probably not introduce an additional measure, but replace the existing memory consumption measure with it.

[philip-stoev]

I think what needs to be measured is the maximum reported from all sources, jemalloc, /proc/, docker stats, you name it. This ensures proper operation in case any of those tends to under-count or not reflect actual or peak usage at all.

[antiguru]

If you have access to metrics, mz_metrics_libc_ru_maxrss on a clusterd reports getrusage's maxrss attribute.

[umanwizard]

I don't think we should use jemalloc stats at all as it can overcount. For example, a very large allocation will count as allocated according to jemalloc but won't result in actual physical memory usage until individual pages are touched. If possible, we should use getrusage as @antiguru suggests.